Hill Climbing

[ROYBUCK]

Just want to run this by some of you, at the present time when I climb a (Hill or Mountain) I let the Allison do the changing or down shift as needed, if it don't down shift at 1400 RPM I will down shift it my self, I haven't had a problem with over heating, just wanted to know if what I am doing is the proper way to handle the Mountain Climbs. A little late to ask since I have been doing it this way for 15 years. It is a 330 ISC 950 Torque at 1400 RPM. Thanks Roy

[Oldme]

Proper RV braking on a downgrade

I agree with this:
"The use of brakes on a long and/or steep downgrade is only a supplement to the braking effect of the engine.
Once the vehicle is in the proper low gear, the following is a proper braking technique:
(1) Apply the brakes just hard enough to feel a definite slowdown. (2) When your speed has been reduced to approximately five mph below your "safe" speed, release the brakes. This brake application should last for about three seconds. (3) When your speed has increased to your "safe" speed, repeat steps 1 and 2". From California DMV.

[wolfe10]

2oldman wrote:

wolfe10 wrote:

2oldman wrote:
Downshifting before the hill is easier on the tranny.

Would like more information on that one-- this is an Allison 3000 series.

When you're already on a hill and your tranny needs to shift, that's more stress than anticipating the hill and shifting sans load. Kinda like downshifting a bicycle derailleur before a hill, because once you're on it, it's pretty hard.

That said, perhaps the Allison etal are really good at shifting under load and it doesn't really matter. I remember my F450s tranny was not a smooth shift under load.

As posted, the Allison is a VERY robust transmission.

Second, there is less stress on it/less HP being generated at peak torque RPM at WOT (wide open throttle) than at higher RPM at the same throttle position. And while climbing, whether on cruise or manual throttle, it will very quickly go to WOT on a grade.

I agree with you, driving a gas rig, particularly one with a high RPM engine such as the very good Ford V10 is VERY, VERY different than a large displacement, turbo, inter-cooled diesel with Allison transmission.

Both Caterpillar and Cummins KNOW that the way to climb a grade using the least amount of fuel is at or just above peak torque RPM even at WOT. And they can sustain that for HOURS (as long as they do not overheat).

[Kidoo]

I found my 300 ISB and 5 speed Alison to work perfectly. I let everything work as it is suppose, never ever had an overheat. It normally stays at 198 F, and on a steep hill, it sometime hits 204 F for very short period.

The only time I use the shifter is to down shift on very steep hills or downhill tight airpin curves along with using the exhaust brake.

[2oldman]

wolfe10 wrote:

2oldman wrote:
Downshifting before the hill is easier on the tranny.

Would like more information on that one-- this is an Allison 3000 series.

When you're already on a hill and your tranny needs to shift, that's more stress than anticipating the hill and shifting sans load. Kinda like downshifting a bicycle derailleur before a hill, because once you're on it, it's pretty hard.

That said, perhaps the Allison etal are really good at shifting under load and it doesn't really matter. I remember my F450s tranny was not a smooth shift under load.

[wa8yxm]

The key word in your original post was "Allison"

That is one of the finest transmissions made (Check that.. It is not "One of the" even FORD says it is the best) and it is smarter than most drivers.. Myself included.

So yes.. letting it do it's thing is a good idea.

Read and undrstand the Grade Brake feature if you have it. Also fantastic.

[rr2254545]

bluwtr49 wrote:
On longish steepish grades I'll normally force a downshift to 5th or even 4th and keep the RPM up to 1800 to 2100 (Cat C-12) or so. This prevents any overheating and it's easy to maintain my speed. 4th at 2100 is about 60 or so.

It's all about what feels good. On not so steep I let the tranny do it's thing and keep the cruise engaged.

x2 I usually go to 4th

[wolfe10]

2oldman wrote:
Downshifting before the hill is easier on the tranny.

Would like more information on that one-- this is an Allison 3000 series. Torque converter is locked in all higher gears.

The only reason I would downshift (down arrow) is if the transmission in hunting between gears or you are overheating.

The OP is doing it EXACTLY correctly (per Cummins): As long as you are not overheating, let RPM lug down to peak torque RPM before downshifting.

[2oldman]

Downshifting before the hill is easier on the tranny.

[bluwtr49]

On longish steepish grades I'll normally force a downshift to 5th or even 4th and keep the RPM up to 1800 to 2100 (Cat C-12) or so. This prevents any overheating and it's easy to maintain my speed. 4th at 2100 is about 60 or so.

It's all about what feels good. On not so steep I let the tranny do it's thing and keep the cruise engaged.

[Trackrig]

To me, it depends on the upcoming grades. If it's just one or two hills, I'll let the Allison do its thing. If I know there is a lot of hill climbing in the next several miles, I'll do the shifting in order to keep the power and RPMS up for cooling. I'll downshift before dropping to 1400 RPMS. I've never had an overheating problem on either the transmission or engine - I like my Scangage.

Bill